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 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
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 */

package javax.sound.sampled;


/**
 * A source data line is a data line to which data may be written.  It acts as
 * a source to its mixer. An application writes audio bytes to a source data line,
 * which handles the buffering of the bytes and delivers them to the mixer.
 * The mixer may mix the samples with those from other sources and then deliver
 * the mix to a target such as an output port (which may represent an audio output
 * device on a sound card).
 * <p>
 * Note that the naming convention for this interface reflects the relationship
 * between the line and its mixer.  From the perspective of an application,
 * a source data line may act as a target for audio data.
 * <p>
 * A source data line can be obtained from a mixer by invoking the
 * <code>{@link Mixer#getLine getLine}</code> method of <code>Mixer</code> with
 * an appropriate <code>{@link DataLine.Info}</code> object.
 * <p>
 * The <code>SourceDataLine</code> interface provides a method for writing
 * audio data to the data line's buffer. Applications that play or mix
 * audio should write data to the source data line quickly enough to keep the
 * buffer from underflowing (emptying), which could cause discontinuities in
 * the audio that are perceived as clicks.  Applications can use the
 * <code>{@link DataLine#available available}</code> method defined in the
 * <code>DataLine</code> interface to determine the amount of data currently
 * queued in the data line's buffer.  The amount of data which can be written
 * to the buffer without blocking is the difference between the buffer size
 * and the amount of queued data.  If the delivery of audio output
 * stops due to underflow, a <code>{@link LineEvent.Type#STOP STOP}</code> event is
 * generated.  A <code>{@link LineEvent.Type#START START}</code> event is generated
 * when the audio output resumes.
 *
 * @author Kara Kytle
 * @see Mixer
 * @see DataLine
 * @see TargetDataLine
 * @since 1.3
 */
public interface SourceDataLine extends DataLine {


  /**
   * Opens the line with the specified format and suggested buffer size,
   * causing the line to acquire any required
   * system resources and become operational.
   * <p>
   * The buffer size is specified in bytes, but must represent an integral
   * number of sample frames.  Invoking this method with a requested buffer
   * size that does not meet this requirement may result in an
   * IllegalArgumentException.  The actual buffer size for the open line may
   * differ from the requested buffer size.  The value actually set may be
   * queried by subsequently calling <code>{@link DataLine#getBufferSize}</code>.
   * <p>
   * If this operation succeeds, the line is marked as open, and an
   * <code>{@link LineEvent.Type#OPEN OPEN}</code> event is dispatched to the
   * line's listeners.
   * <p>
   * Invoking this method on a line which is already open is illegal
   * and may result in an <code>IllegalStateException</code>.
   * <p>
   * Note that some lines, once closed, cannot be reopened.  Attempts
   * to reopen such a line will always result in a
   * <code>LineUnavailableException</code>.
   *
   * @param format the desired audio format
   * @param bufferSize the desired buffer size
   * @throws LineUnavailableException if the line cannot be opened due to resource restrictions
   * @throws IllegalArgumentException if the buffer size does not represent an integral number of
   * sample frames, or if <code>format</code> is not fully specified or invalid
   * @throws IllegalStateException if the line is already open
   * @throws SecurityException if the line cannot be opened due to security restrictions
   * @see #open(AudioFormat)
   * @see Line#open
   * @see Line#close
   * @see Line#isOpen
   * @see LineEvent
   */
  public void open(AudioFormat format, int bufferSize) throws LineUnavailableException;


  /**
   * Opens the line with the specified format, causing the line to acquire any
   * required system resources and become operational.
   *
   * <p>
   * The implementation chooses a buffer size, which is measured in bytes but
   * which encompasses an integral number of sample frames.  The buffer size
   * that the system has chosen may be queried by subsequently calling
   * <code>{@link DataLine#getBufferSize}</code>.
   * <p>
   * If this operation succeeds, the line is marked as open, and an
   * <code>{@link LineEvent.Type#OPEN OPEN}</code> event is dispatched to the
   * line's listeners.
   * <p>
   * Invoking this method on a line which is already open is illegal
   * and may result in an <code>IllegalStateException</code>.
   * <p>
   * Note that some lines, once closed, cannot be reopened.  Attempts
   * to reopen such a line will always result in a
   * <code>LineUnavailableException</code>.
   *
   * @param format the desired audio format
   * @throws LineUnavailableException if the line cannot be opened due to resource restrictions
   * @throws IllegalArgumentException if <code>format</code> is not fully specified or invalid
   * @throws IllegalStateException if the line is already open
   * @throws SecurityException if the line cannot be opened due to security restrictions
   * @see #open(AudioFormat, int)
   * @see Line#open
   * @see Line#close
   * @see Line#isOpen
   * @see LineEvent
   */
  public void open(AudioFormat format) throws LineUnavailableException;


  /**
   * Writes audio data to the mixer via this source data line.  The requested
   * number of bytes of data are read from the specified array,
   * starting at the given offset into the array, and written to the data
   * line's buffer.  If the caller attempts to write more data than can
   * currently be written (see <code>{@link DataLine#available available}</code>),
   * this method blocks until the requested amount of data has been written.
   * This applies even if the requested amount of data to write is greater
   * than the data line's buffer size.  However, if the data line is closed,
   * stopped, or flushed before the requested amount has been written,
   * the method no longer blocks, but returns the number of bytes
   * written thus far.
   * <p>
   * The number of bytes that can be written without blocking can be ascertained
   * using the <code>{@link DataLine#available available}</code> method of the
   * <code>DataLine</code> interface.  (While it is guaranteed that
   * this number of bytes can be written without blocking, there is no guarantee
   * that attempts to write additional data will block.)
   * <p>
   * The number of bytes to write must represent an integral number of
   * sample frames, such that:
   * <br>
   * <center><code>[ bytes written ] % [frame size in bytes ] == 0</code></center>
   * <br>
   * The return value will always meet this requirement.  A request to write a
   * number of bytes representing a non-integral number of sample frames cannot
   * be fulfilled and may result in an <code>IllegalArgumentException</code>.
   *
   * @param b a byte array containing data to be written to the data line
   * @param len the length, in bytes, of the valid data in the array (in other words, the requested
   * amount of data to write, in bytes)
   * @param off the offset from the beginning of the array, in bytes
   * @return the number of bytes actually written
   * @throws IllegalArgumentException if the requested number of bytes does not represent an
   * integral number of sample frames, or if <code>len</code> is negative
   * @throws ArrayIndexOutOfBoundsException if <code>off</code> is negative, or <code>off+len</code>
   * is greater than the length of the array <code>b</code>.
   * @see TargetDataLine#read
   * @see DataLine#available
   */
  public int write(byte[] b, int off, int len);

  /**
   * Obtains the number of sample frames of audio data that can be written to
   * the mixer, via this data line, without blocking.  Note that the return
   * value measures sample frames, not bytes.
   * @return the number of sample frames currently available for writing
   * @see TargetDataLine#availableRead
   */
  //public int availableWrite();
}
